The present invention relates to a method of preventing a weft yarn having a defect therein from being woven in a fabric in a shuttleless weaving machine such as air jet loom.
In a conventional shuttleless loom which uses fluid as the means for picking the weft yarn into the shed, it has been customarily performed that a woven fabric is inspected visually during the weaving operation of the loom for containing therein a defective weft yarn and the weaving operation is interrupted if such a faulty weft is recognized so that the weft having the fault may be removed from the fabric, whereupon the loom operation is resumed. However, since the visual inspection is made only after the defective yarn has been inserted and beaten up and therefore held firmly in the woven cloth, the removal of the defective yarn therefrom may be accomplished only by an extremely difficult and time-consuming operation during which the loom weaving operation needs be kept stopped, which will invite quite a decrease in the operational efficiency of the loom. According to another known method, a defect is recognized by detecting a yarn break resulting from such a defect and the defective weft yarn is removed for disposal thereof. In this method, however, the weft yarn containing a defect which does not result in a break thereof will be inserted through a shed and thus woven in the fabric. In this way, this method cannot cope with the problems associated with the fabric quality in that a defective weft yarn is woven in the product fabric. That is, this method is unable to avoid the deterioration of the fabric quality.